The present invention relates to an electrophotographic system comprising an electrophotographic copying apparatus and an option device for forming an enlarged or reduced image of a document set in the option device.
The copying apparatus represented by an electrophotographic copying apparatus has practically been used in many ways for the purpose of copying documents, and almost all of the copying apparatuses are constructed to obtain a copy of the same size from sheet-like and book-like documents. On the other hand, there has been known such apparatus that a reduced image of a large size document is printed or an enlarged image of a microfilm is printed in an electrophotographic manner, but such apparatus is assembled in a copying apparatus with the inseparable form or in case of using it as an option device, use is made of the same optical path as that of the copying apparatus itself or use is made of a part of an optical path of the copying apparatus itself in common. It is common technique to assemble a reduction optical system in the copying apparatus itself inseparably, but the thus assembled apparatus becomes large and complicated. It is further known to detachably add an optical image projector to the copying apparatus itself as an option device, but such apparatus also has various defects. For example, in Japanese Patent Application Publication No. 4,944/67. Japanese Patent Application Publication No. 8,437/69, Japanese Patent Laid-open No. 62,724/76, Japanese Utility Model Laid-open No. 127,827/77, Japanese Patent Laid-open No. 55,647/77 and the like, there is disclosed that the whole frame of a microfilm image is projected on a document table or a photosensitive member as a still picture by an option device and the projected image is scanned and exposed in the former apparatus by a scanning optical system, while in the latter apparatus the projected image is directly converted into an electrostatic latent image. However, the copying apparatus for copying the whole frame of a microfilm image projected as a still picture is large as the apparatus itself and lack universality and convenience as compared with the copying apparatus of a document moving, scanning and exposing type which has recently been often used. In the former system for projecting the microfilm image on the document table, when an enlarged image is projected by an option device, it is necessary to provide a long optical path in the device, so that the option device becomes disadvantageously large.
Further in case of using an electrophotographic copying apparatus of a slit exposure and scanning type in which the document to be copied is moved at a given constant speed with respect to a scanning optical system, it is required to construct the option device also as the slit exposure and scanning type. In such a case if a feeding direction of document inserted in the option device is made different from the feeding direction of document inserted in the copying apparatus, a user might confuse in handling the document to be copied. For instance, if the document feed direction in the option device is reversed to that in the copying apparatus, a relation between postures, i.e. front and rear, and right and left of documents and duplicated copies becomes reversed for the duplication with and without the option device. Therefore, the operator has to remember the above relation and has to insert the documents with taking into account the relation. This is quite inconvenient for the operator. Therefore, it is quite desirable to construct the option device into which the document can be inserted in the same direction as that of the document feed in the copying apparatus.
In case of detachably mounting the option device on the copying apparatus, it is desired that the document inserted in the copying device can be duplicated without removing the option device in order to improve the useful function of the duplicating system. In the known systems, since the document table of the copying apparatus is almost covered or hindered by the option device, the operator could not see well the document table of copying apparatus and feels difficult in handling the document. Further in many copying apparatuses, operating members such as a copy start button, stop button, copy number selector, and various indicating lamps are usually arranged on a front panel or a top panel and thus, when the option device is mounted on the copying apparatus, these operating members and indicating lamps might be hindered by the option device. In order to avoid such a drawback, it is necessary to shift the option device with respect to the copying apparatus in a direction perpendicular to the document feed direction.
Moreover it should be noted that in order to reduce the size and cost of the option device, it is desirable not to provide in the option device a driving source for feeding the document inserted into the option device. This can be achieved by driving the document feeder of the option device by means of a driving source provided in the copying apparatus for feeding the document inserted into the copying apparatus. Moreover in such known electrophotographic duplicating systems comprising the electrophotographic apparatus and the option device for projecting the enlarged or reduced image of document, it is impossible to control the option device commonly by means of a sequence control circuit for controlling a duplicating operation of the copying apparatus without the option device, because the image of document is projected from the option device onto a photosensitive member of the copying apparatus from a position which is different from an imaginary control start position of the photosensitive member in case of normal duplicating operation without the option device. Therefore, it is necessary to provide a separate sequence control circuit. This causes the duplicating system complicated in construction and expensive in cost.